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    <title>Document</title>
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    <div>
        上午好
    </div>
    <script>
        var div = document.querySelector('div');
        var date = new Date();
        var h = date.getHours();
        if (h < 12) {
            div.innerHTML = '上午好';
        } else if (h < 18) {
            div.innerHTML = '下午好';
        } else {
            div.innerHTML = '晚上好';
        }
    </script>
</body>

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